Patent Literature (PTL) 1 discloses a stacked solid-state imaging device. The stacked solid-state imaging device disclosed in PTL 1 generates noise in resetting signal charge. Specifically, if the shape of a reset pulse in pulse-off time is steep, whether the charge on a channel is transferred to a source or a drain of a reset transistor is determined at random. Thus, the transferred charge appears as kTC noise. The kTC noise is also generated by capacitive coupling between a reset signal line and a pixel electrode, for example.
Moreover, the stacked solid-state imaging device cannot completely cancel the kTC noise, even with use of correlated double sampling. This is because complete transfer of electrical charge is not allowed due to a fact that a photoelectric conversion unit above a semiconductor substrate and the semiconductor substrate are connected by a conducting material such as a metal. After signal charge is reset, the subsequent signal charge is added thereto while the kTC noise remains. Thus, signal charge having the kTC noise superimposed thereon is read out. The solid-state imaging device disclosed in PTL 1, therefore, has a problem of an increased kTC noise.
A technique as disclosed in PTL 2 is proposed to reduce the kTC noise.
FIG. 14 is a diagram showing a unit pixel disclosed in PTL 2 and its peripheral circuit. In the solid-state imaging device shown in PTL 2, a reset of signal charge generated by photodiodes 512 is initiated by completely turning on row selection transistors 518 of unit pixels 510 in a selected row. Here, one terminal of each of amplifier transistors 514 included in all the unit pixels 510 in the selected row is connected to a low impedance voltage source within a source power 530 via a column signal line 524. A transistor 520 connected to a power line 522 is biased as a current source by a waveform Vbias of a gate 526. The amplifier transistor 514 and the transistor 520 constitute an amplifier having negative gain. The channel resistance of a reset transistor 516 varies depending on a step-down reset power 550. Specifically, application of a reset pulse that has a ramp waveform generated from the step-down reset power 550 to a gate of the reset transistor 516 gradually increases the channel resistance of the reset transistor 516. Bandwidth of the kTC noise generated in the reset transistor 516 is inversely proportional to the channel resistance of the reset transistor 516, reducing the bandwidth of the kTC noise as the channel resistance increases. Thus, if the bandwidth of the kTC noise is reduced to a bandwidth of the amplifier configured of the amplifier transistor 514 and the transistor 520, the kTC noise is effectively suppressed due to negative feedback from the amplifier.